1. FIELD OF THE INVENTION
This invention relates to a routing control method in a data switching network, and more specifically to an adaptive routing method permitting to take measures against occurrence of load fluctuations or obstructions.
2. DESCRIPTION OF PRIOR ART
Recently a data switching network, more specifically a packet switching network has been adopted in many data communication networks such as VAN (value-added network) and so forth. In a packet switching network, unless each switching node has any information about the circumstances of the network, it is required that it send messages (packets) through each of the routes at random, because it cannot select the optimum route to the destination station, and naturally this gives rise to a problem such as delay in transmission of information, etc. Consequently adaptive routing techniques permitting the selection of the optimum route, depends on the condition of the network for implementing a packet switching network.
Concerning the adaptive routing method, heretofore, various studies have been reported e.g. in Routing Techniques for Store-and-Forward Computer-Communication Networks, ICC, 1971 by G. L. Flutz and L. Kleinrock. However, according to the prior art adaptive routing method, since updating of the estimated delay at the center has been effected only when some obstructions have occurred or when the network configuration has been modified and since the estimated delay has not depended on the load of each of the switching nodes but has been fixed in the cases other than those described above, selection of the route has been effected, taking into account the load at the switching node determining the route, but without taking into account the load at relay switching nodes receiving messages.